Safety switch for internalcombustion engines



July 20, 1948 l c. L. MEINHLDT 2,445,625

SAFETY SWITCH FOR INTERNALCOMBUSTION ENGINES Filed Jan. 26, 1945 30 Arron/vn; A

Patented July 20, 1948 SAFETY SWITCH FOR INTERNAL- COMBUSTION ENGINES Charles L. Melnholdt, Topeka, Kans.

Application January 26, 1945, Serial No. 574,798

(Cl. 20G-140) 2 Claims. 1

responsive to temperature of the cooling liquid; l

to provide a safety device that is of inexpensive construction and which is adapted to be installed in any one of the usual plugged openings of a cylinder head or block of an engine; to provide a safety device equipped with electrical contacts for connection with the electrical or other supply system which maintains operation of an engine;

and to provide a. safety device that is adjustable to actuate at a selected temperature.

In accomplishing these and other objects of the invention, I have provided an improved structure, the preferred form of which is illustrated in the accompanying drawing wherein:

Fig. 1 is a perspective view of a safety device constructed in accordance with the present invention and applied to the head of an internal combustion engine and which is shown as connected with the ignition system, the ignition system being illustrated in diagram.

Fig. 2 is a vertical section through the safety device.

Fig. 3 is a perspective View of the parts of the safety device shown in disassembled spaced relation.

Referring more in detail to the drawing:

I designates a safety device constructed in accordance with the present invention and which is especially designed for mounting in one of the plugged openings 2 that are usually provided in the head 3 of an internal combustion engine 4 so that it is energized when the working temperature of the engine reaches a predetermined maximum to suspend operation of the electrical system and thereby render the electrical system sumciently ineffective to stop operation of the engine.

The safety device includes a shell 6 having an externally threaded wall portion 1 adapted to be threaded in the opening 2 and having an upper hexagonal portion 8 to be engaged by a wrench or the like for turning the shell into the opening. The shell 6 has a, through bore 9 forming a chamber III for containing an accordion-type bellows I I, one end of which is rigidly attached relative to 2 the shell by an annular ring I2 having a flange portion I3 seated upon an internal annular seat I4 of the bellows chamber, the ring being soldered to the shell as at I5 to form a gas-tight seal therearound. The lower end of the bellows carries a piston-like guide I6 that is slidable in the shell and adapted to shift a contact element I1 into engagement with a fixed contact element I8 later described. The contact element I1 includes a rod-like stem I9 having a reduced portion 2G sealed within an axial opening 2l of the piston-like guide to support the opposite portion of the rodlike guide coaxially within the bellows so that it projects through the anchoring ring I2. The piston-like guide normally seats upon an annular shoulder 22 that is formed by an internally extending flange 24 on the inner face of the shell as shown in Fig. 2. Sleeved within the open end of the bore on the side of the flange opposite the shoulder 22 is a bulb element 25 for containing an expansive fluid indicated at 26. rhe bulb 25 is formed of a cylindrical sleeve 21 formed of relatively thin material so as to provide rapid heat conduction therethrough to the expansive iiuid contained therein. The sleeve is suitably retained within the open end of the shell to form a fluidtight joint as by soldering or the like as indicated at 28. The lower end of the sleeve is closed by an inset head 29 sealed therein by soldering or the like 30. The head 29 may have a fill opening 3l through which the expansive fiuid is inserted in the bulb and which is adapted to be closed to retain the heaty expansive fluid by a ball valve 32 and a sealing material such as solder 33 that closes the outer open end of the opening 3|.

The opposite end of the shell is closed by an insulating head 34 having the periphery 35 thereof seated upon an internal shoulder 3B and the hexagonal portion of the shell and which is retained thereon by turning over the rim 31 as shown in Fig. 2. Carried within an opening 38 of the insulator 34 and coaxially with the contact element I1 is an internally threaded bushing 39 mounting the contact element I8. The bushing 39 includes a head portion 40 engaging the outer side of the insulating head and which has a neck portion 4I extending through the opening 38 of the head and which has an edge 42 turned over the inner face of the head to securely anchor the bushing therein. f

The contact element I8 comprises an externally threaded stud mounted/in a threaded axial opening 43 of the bushing and carries a lock nut 44 which is adapted to be turned against the bushing after the threaded contact element has 'been adjusted relative to the movable contact element I9 to provide a proper spacing 45 therebetween so that the bellows may operate responsive to expansion and contraction of the fluid V26 under the Apropel' working temperatures of the engine without causing the engagement of the contacts. The outer end of the threaded contact element carries a terminal 46 that is suitably shaped to connect a snap socket 41 of an electrical conductor 48 which isadapted to be connected with the electrical system to ground the ignition circuit through the shell 6 of the safety device. l

In assembling the safety device, the sleeve 21 forming the bulb 25 is inserted in the open end of the threaded portion 1 of the shell 6 and sealed therein by the solder 28. 'I'hen the bellows carrying the guide I6 and anchoring ring I2 is inserted through the opposite end of the shell so that the flange I3 on the ring I2 seats upon the shoulder 42 with the guide 2| resting on the shoulder 22. The ring I2 is then sealed in position by the solder I5. The insulating head 34 carrying the bushing 39, threaded contact element I8, and the lock nut 44 is applied to the shell 6 so that the periphery thereof seats against theshoulder 36. The outer projecting portion 31 of the shell is then turned over the outer face of the insulating head 34 as shown in Fig. 2. The bulb is then filled through the opening 31 with an expansive fiuid which is adapted to operate the bellows when the Working temperature of an engine protected by the safety device reaches a predetermined maximum.

After filling y,of the bulb, the opening is sealed by the solder 33. The safety device is readily applied to an engine by unscrewing the plug (not shown) which normally closes the internally threaded opening 2. The safety device is then applied by inserting the bulb portion thereof through the opening 2 and turning the shell of the safeaty device so that the threads 1 engage the threads of the opening v2.

When in position, the bulb 25 projects within the water space of the cylinder head and is entirely surrounded with the cooling liquid when the cooling liquid supply is adequate. 'I'he contact element I8 is then adjusted relative to the movable contact element I1 to provide a desired space-45 therebetween. After adjustment, the lock nut is tightened to engage the bushingr so as to prevent rotation of the fixed contact element. The conductor 48 is then applied to the head 46 and connected with the electrical system so as to provide a ground through the shell 6 of the safety device whenever the contact I1 carried by the bellows engages the end of the fixed contact I8.

In operation, the spacing 44 will be maintained between the contact elements I1 and lIIB under normal working temperatures of the engine; however, should the cooling water rise above a predetermined temperature, the expansion of the iiuid in the bulb acts on the lower end of the bellows to bring the movable contact I1 into engagement with the fixed contact 'element I8, thereby providingV a direct ground through the cylinder head 3 to caus'e suspension of theV engine operation the temperature falls within the working temperature range.

It is thus obvious that should the supply of cooling liquid become exhausted so that the engine tends to operate above the normal working temperature, the safety device will function to until such a time thatV stop operation thereof: likewise if the fan belt should become loose so that the fan does not properly cool thev cooling liquid, the safety device will function; or the safety device will function in case of an inadequate lubricant supply; ineffective cooling of the cooling liquid, or for many other causes which are apt to be injurious to the engine should the engine continue to operate.

.If desired, the safety device may be used as a switch for closing circuit to a signal which would indicate too high engine temperature without' stopping the engine.

While I have particularly illustrated the invention as applied to an internal combustion engine, it is obvious that the device may be used in connection with any heat transmitting body which requires the' use of a cooling liquid or wherein the bulb portion is adapted' to be located in a position to be responsive totemperature of the heat transmitting body.

What I claim and desire to'secure by Letters Patent is: v y

1. A safety device including a shell having an end adapted for mounting in an opening of an internal combustion engine, a bulb connected with said end of the shell and projecting coaxially therefrom for emersion in cooling liquid of the engine, said shell having axially spaced shoulders inset from the opposite end of the shell, a bellows in the shell having open and closed ends and adapted to be operated by heat responsive medium in said bulb, said open end of the bellows having an annulus engaging the inner of said shoulders, sealing means fixing the annulus to the shell for retaining the heat responsive medium, an insulator seated on the outer shoulder of the shell, a .fixed contact carried by the ins'ulator, a movable contact carried by the closed end of the bellows and extending coaxially through the bellows to project from the open end in registry with the fixed contact and adapted' tovengage the fixed ,contact responsive to contraction of the bellows by the heat responsive medium in said bulb, a guide on the closed end of the bellows and adapted for sliding contact with the shell during contraction of the bellows to retain said movable contact in coaxial alignment with the fixed contact, and means on the shell for retaining the insulator on the outer of said shoulders;

2. A safety device including a shell having an end adapted for mounting in an opening of an internal combustion engine, a bulb connected with said end of the shell and projecting coaxially therefrom for emersion in cooling liquid of the engine, said shell having axially spaced shoulders inset from the opposite end of the shell, a bellows in the shell having open and closed ends and adapted to be operated by heat responsive medium in said bulb, said open end of the bellows having an annulus engaging the inner of said shoulders. sealing means fixing the annulus to the shell for retaining the heat responsive medium. an insulator seated on the outer shoulder of the shell, a fixed contact carried by the insulator, a movable contact carried by the closed end of the bellows and extending coaxially through the bellows to project from the open end in registry with the fixed contact and adapted to engage the fixed contact responsive to contraction of the bellows by the heat responsive medium in said bulb. a guide on the closed end of the bellows and adapted for sliding contact with the shell during contraction of the bellows to retain said movable contact in coaxial alignment with the fixed contact,

MIJIB mem on the shell for retaining the insulator on the cuter or ma shoulders, and s nos mma mmm STATES ma shell for contact by the guide to support the Number Name Date closed end of the bellows when the contacts are in 1,342,317 Wireu June 1, 1920 spaced relstion. 1,386,844 Cowen Aug. 9, 1921 cHARLEsL MmNHoLUr. 1,908,088 warner May 9. 1933 2,195,744 Emerson Apr. 2, 1940 REFERENCES CITED The following references are of record in the u 111e o! this patent: 

